Describe the memory that Jonas is receves at the beginning of Chapter 15 in The Giver. Why does the Giver say "forgive me?"

The Giver knows that the memory that he is going to transfer to Jonas will be unique to him.  Until now Jonas has only had good memories with the exception of sunburn.  He has not experienced death and the horrors of war.

The Giver transfers the memory of the battle field to Jonas.  Jonas sees the he young soldier dying and the fear that it includes.  He is horrified for the first time.  He knows the pain of death, fear, terror, and all the awful things that go with a war.  It is a transition point for Jonas who now knows that death is a bad and painful experience.

Later when he sees his friend playing a war game, he tells him to stop.